Fix the bug of next_point in source_map There is a bug in `next_point`, the new span won't move to next position when be called in the first time. For this reason, our current code is working like this: 1. When we really want to move to the next position, we called two times of `next_point` 2. Some code which use `next_point` actually done the same thing with `shrink_to_hi` This fix make sure when `next_point` is called, span will move with the width at least 1, and also work correctly in the scenario of multiple bytes. Ref: https://github.com/rust-lang/rust/pull/103140#discussion_r997710998 r? `@davidtwco`